Method and apparatus for producing bulged shapes



Oct. 15, 1968 B. L. HOFFMAN ET AL METHOD AND APPARATUS FOR PRODUCINGBULGED SHAPES 5 Sheets-Sheet 2 AON , O @a E NVENTORS @e9/veen L. Hof-FM4BY L//vcouv 966D PTM/Maffe@ @L Oct. 15, 1968 B. L. HOFFMAN ET AL.3,405,546

METHOD AND APPARATUS FOR PRODUCING BULGED SHAPES Filed Sept. 27, 1965 5Sheets-Sheet 5 1N VENTORS 564mm) L Hoff-MAN BY meow C. ,P660

Oct. 15, 1968 a. L. HOFFMAN ET AL 3,405,546

METHOD AND APPARATUS FOR PRODUCING BULGED SHAPES 5 Sheets-Sheet 4 FiledSept. 27, 1965 IN VEN TORS MM fag/16%@ Oct. 15, 1968 B. l.. HOFFMAN ETAL 3,405,546

METHOD AND APPARATUS FOR PRODUCING BULGED SHAPES Filed Sept. 27, 1965 5Sheets-Sheet 5 qo\\l\ Si vo l N VEN TRS Ba/wwo HOFFMAN 3,405,546 METHODAND APPARATUS FOR PRODUCING BULGED SHAPES Bernard L. Hoffman, Trenton,and Lincoln C. Reed,

Finesville, NJ., assignors to Frederick A. Krause Associates, Inc.,Frenchtown, NJ., a corporation of New Jersey v Filed Sept. 27, 1965,Ser. No. 490,222 9 Claims. (Cl. 72--348) ABSTRACT OF THE DISCLOSUREPress arrangements for producing bulged container shaped objects whereina retractable forming ring rst forms the container shaped object bypassing over a central mandrel, and is then retracted to define anannular bulging region at a given location.

This invention relates to the forming of sheet metal and moreparticularly it concerns the production of bulged drawn objects.

Drawing and stamping of sheet metal to produce various shaped objects iswell known. There are many advantages .to such processes; and of latethey have come into quite extensive use.

One drawback `of known drawing and stamping tech- 'niques is that theydo not lend themselves well to the production of bulged shapes. In thepast, in order to form objects having a bulged configuration, the objecthad to be fully processed or at least finished by spinning as on a lathetype tool. Conventional stamping or drawing processes, while suitablefor converting flat sheet metal into container shapes with straight(parallel) sides or outwardly ared sides, were incapable of convertingilat metal workpieces into container shapes which had reverse tapers orwhich had internal cross sectional dimensions larger than the crosssection of the mouth or top opening of the object being formed.

The reason why bulged shapes could not be produced United States PatentO in conventional stamping operations is that the mating die elementsmoved only along a single path (usually vertically) toward and away fromeach other. The formation of a bulged object, however, requires themovement of metal in two orthogonal directions i.e. vertically andlaterally. Known dies which move only in a vertical direction cannotmove metal laterally to form bulges; and even if they could, there wouldbe a problem of extracting the `expanded or laterally moved die outthrough the smaller 'opening at the mouth of the object after itsformation.

The present invention makes possible the production of bulged shapes indrawn sheet metal objects in a single drawing operation. The presentinventionv requires no specially complex die elements, nor does itrequire any intricate devices for obtaining lateral deformation of themetal.

According to the present invention, bulges are provided in sheet metalby providing the metal with complete lateral support on one side, andlateral support on the opposite side over all but the region of thebulge. The metal thus laterally supported is then subjected tocompressive stresses in the plane of its extension. These stressesconcentrate in the unsupported region where the bulge is to occur, witha consequent straining and bulging of the metal in this region.

As illustratively embodied, the present invention makes use of upper andlower die assemblies each having a plurality of extendible die elements.These die assemblies are first brought together so that their respectivedie elements form a sheet metal workpiece into a general containershape. This bringing together of the die elements 3,405,546 PatentedOct. 15, 1968 ICC on the upper and lower die assemblies simultaneouslyserves to provide lateral support all along the inner and outer surfacesof the sides of the container shaped workpiece. One of the die elementsis then retracted to remove lateral support from the region of theworkpiece which is to be bulged. Thereafter the die assemblies continueto move toward each other with one pushing against the extreme edge ofthe workpiece to provide compression in its plane of extension. As aresult, the workpiece will become bulged into the unsupported regionvacated by the retracted die element.

The present invention, as will be described more fully hereinafter, incertain aspects makes special use of novel hydraulically retractible dieelements andv specially shaped die elements which apply compressiveforces in a proper direction for controlled bulging.

The present invention in other aspects makes use of semi-fluid materialsin a novel manner in the supporting region opposite the region to bebulged and causes this material to ow laterally to induce the bulging ofthe workpiece material in a more controlled manner.

There has thus been outlined rather broadly the more important featuresof the invention in order that the detailed description thereof thatfollows may be better understood, and in order that the presentcontribution to the fart may be better appreciated. There are, ofcourse, additional features of the invention that will be describedhereinafter and which will form the subject of the claims appendedhereto. Those skilled in the art will appreciate that the conceptionupon which this disclosure is based may readily be utilized as a basisfor the designing of other structures for carrying out the severalpurposes of the invention. It is important, therefore, that the claimsbe regarded as including such equivalent construction as do not departfrom the spirit and scope of the invention.

Specific embodiments of the invention have been chosen for purposes ofillustration and description, and are shown in the accompanyingdrawings, forming a part of the specification, wherein:

FIG. l is a fragmentary section view taken in elevation, along with aschematic hydraulic diagram illustrating an apparatus embodying thepresent invention as it appears at the beginning of its operation;

FIG. 1A is a perspective view showing a workpiece prior to entry intothe apparatus of FIG. l;

FIG. 2 is a fragmentary section view similar to FIG. 1 but showing onlyone-half of the apparatus of FIG. 1 as it appears after a first portionof its operation;

FIG. 2A is a perspective view of the workpiece of FIG. 1 as it appearsat the stage of operation illustrated in FIG. 2;

FIG. 3 is a view, similar to FIG. 2, of the apparatus las it appearsafter a further portion of its operation;

FIG. 4 is a view, similar to FIG. 2, of the apparatus as it appearsafter a still further portion of its operation;

FIG. 4A is a perspective view of the workpiece of FIG. l as it appearsat the stage of operation illustrated in FIG. 4;

FIG. 5 is `a view, similar to FIG. 2, of the apparatus as it appearsafter its nal stage of operation; and

FIGS. 6-9 are views similar to FIGS. 2-4 showing a modified version ofthe apparatus in various stages of its operation.

As shown in FIG. 1, there is provided a novel die assembly, indicatedgenerally at 10, and comprising upper and lower die shoes 12 and 14,arranged in a press (not shown) so as to be moved toward and away fromeach other in a vertical direction.

The die shoes 12 and 14 have mounted on their mutually facing surfacesvarious fixed Iand movable die elements; and these die elements act upona sheet metal workpiece 16 positionedtherebetween to perform'various t'fposela umber of bulging'ri drawing and bulging operations to bedescribed. Y d The various die elementsare of Ycircular configuration.Thus for purposes of detail, all central portions of the die assemblyhave been cut away in the illustrative drawings.

The various die elements on the upper die shoe 12v are larranged inconcentric relationship; and beginning at the outside they include anupper shear ring element 18 fixed to the die shoe, a retractable dieelement`20 movable on the upper die shoe, an upper hold down ring 22,movable on the die shoe, and an upper stop member 24 fixed cen trally ofthe die shoe. l

An annularly shaped retraction piston' 26 is mounted for verticalreciprocal movementl in a similarly shaped hydraulic passageway 28 inthe upper die shoe 12.4 This piston is formed with a rod 30 whichextends out through the bottom of the upper die'shoe 12 and connectswith the retractable die element 20 to control the movements j of thiselement on the upper die shoe.

There is also provided an annularly shaped hold down ring actuatingpiston 32 arranged in a similarly shaped hydraulic passageway 34 in theupper die shoe 12; and this piston is connected to control the movementsof the upper hold down ring 22 with respect to the upper die shoe 12.

The hydraulic passageway 34 for the hold down ring actuating piston 32is connected at the upper end thereof through a first hydraulic channel36 and a first hydraulic supply line 38 to a pressurized hydraulicsupply unit, indicated schematically at 40. This unit may be of the typedescribed in a copending application entitled Pressurized Fluid SupplySystem, Ser. No. 340,439, filed I an. 27, 1964. Its essential purpose isto maintain sufficient fluid in the hydraulic channel 36 and thepassageway 34 to force the hold down ring .actuating piston 32downwardly during au initial portion of the closing of the die shoes;and when the resistance against the upper hold down ring 22 reaches acertain value, for example, suicient to raise the hydraulic pressureabove 4500 p.s.i., then the hydraulic supply unit 40 will admit thefluid displaced by the re tracting piston 32 while maintaining the 4500p.s.i. pressure.

The other hydraulic passageway 28 for the retraction piston 26 isconnected at its upper and lower ends respectively through second andthird hydraulic channels 42 and 44 and associated hydraulic supply lines46 and 48 and a double action control valve 50 to the hydraulic -..moana`g support rods 66'which-extend from the bottom of the bulging dieelement 62 to a yoke 68 which is moved by a common bulging die pistonsupply unit 40. Initially the valve is set as shown in v FIG. l so thathigh pressure is directed through the second hydraulic channel 42 to thetop of the retraction piston 26 causing it to force down the retractabledie element 20. Thereafter, the valve 50 is switched so that highpressure is applied to the under side of the retraction piston 26causing it to rise and retract the retractable die element 20.

It will be noted vfrom the drawings that the upper shear ring element 18and the upper stop member 24, both of which are fixed to the upper dieshoe 12, are each provided with overhanging lips 52 and 54 which areengaged respectively by flanges 56 and 58 on the upper hold down ring 22and the retractable die element 20 to restrict their movements withrespect to the upper die shoe 12.

The die elements on the lower die shoe 14 are also arranged inconcentric relationship and are coaxially aligned with theircounterparts on the upper die shoe 12 for intermeshing therewith as theshoes are brought together. These lower shoe die elements, beginning atthe outside, include a lower shear ring element 60, a bulging ringelement 62 and a central forming mandrel 64. The lower shear ringelement 60 and the central forming mandrel 64 are both xed to the upperface of the lower die shoe 14, while the bulging ring element 62 isreciprocally movable thereon. There are provided for this pur- 70.Hydraulic means, as described above in connection with the upper dieshoe 12, are provided to actuate the bulging die piston 70. Y

Asstated, above, .the various die4 elements areddimensioned 'andarranged to t into intermeshing'relationship as the die shoes.4 12 and14 are moved together. Thus, the,.re,tractable die element 20. onftheuppershoe,-12 is dimensioned'to-lit over the central forming mandrel- 64on the lower die shoe 14, but with suicient clearance to allow apartially formed workpiece to extend therebetween. Also, the upper andlower shear ring elements 18 and 60 are provided with closely matingshear corners 72 which cooperate toy trim the workpiece 1 6, prior toforming. Further,`the bulging die element 62is provided witha'stepcorner cutout about its upper inside corner to control the bulgingoperation as hereinater described.

During operation of the device, the upper and lower die'shoes 12 and 14are closed or `brought together about the workpiece 1-6. The crosssectional area of the bulging die piston 70 is smaller than the area ofthe retraction piston 26. Thus, during the initial portion of the dieshoe closure'movement, the bulging die element 62 yields to the force ofthe upper shear ring element 18 and the retractable die element 20 asthese two elements descend into the annular region'between the centralforming mandrel 64 and the lower shear ring element 60.

The workpiece 16, which initially may be o'f rectangular conligurationas shown in FIG. 1A, is sheared by the shear corners 72 of the shearring element 60. As the die shoes continue to come together, asillustrated in FIG. 2, the bulging die element 62 cooperates with theupper shear ring element 18 and the retractable die element 20 tosqueeze the workpiece between it and them as it-is forced down bythem;"l`his serves to maintain the workpiece Imaterialliat `as it isbeing worked over the central forming mandrel 64 into an inverted cupshaped member as indicated at 76 in FIG. 2A. This serves to preventwrinkling and thus ensures a uniform smooth surfaced end product.

At this point in the operation of the device,'the die shoes 12 and 14are brought together to their fullest extent. The control valve 50 isthen operated to reverse the-application of hydraulic pressure from thesecond hydraulic channel 42l to the-third channel 44. This reversal inapplication of hydraulic pressure to the retraction piston 26 acts'toforce it upward along with the retractable die element 20 as shown inFIG. 3. The retraction of the retractable die element 20 leaves a void78, for the bulging die element 62 continues to be held down by theupper shear ring element 18.

The bulging operation takes place upon opening of the die shoes 12 and14. During this opening, as illustrated in FIG. 4, the upper shear ringelement 18, which is fixed to the upper die shoe 12, is raised alongwith the upper die shoe. This allows the bulging die element 62 to moveupwardly with it. The corner cutout 74 of the bulging die elementeventually engages the lower edge of the inverted cup shaped member 76formed from the workpiece 16. The upward movement of the bulging dieelement thus exerts a compressive stress on the wall of the cup shapedmember 76 in its plane of extension. This compressive stress ismaintained on top of the cup shaped member 76 even while the die shoesare being opened due to the continuous hydraulic pressure in the firsthydraulic channel operating through the hold down ring actuating piston32 to force the upper hold down ring 22 against the upper surface of themember 76. An outer flange 80 onthe hold down ring engages theretractable die element 20 causing its lower edge to remain lush withthe lower edge of the hold down ring 22 so that the contiguration of thevoid 78 remains the same during the opening of 'the die shoes.

It will lbe noted that at this point, the entire inner surface of thecup shaped member 76 is laterally 'supported by the central formingmandrel 64. Also, the upper regions of the member 76 are supported bythe hold down ring 22 and the retractable die element 20; and the lowerregion of the outside surface of the cup shaped member is supported by.the step corner cutout 74 of the bulging die element. Thus, the onlylaterally unsupported Iregion of the cup shaped member is at the void 78into which a bulge is to be formed.

As the die shoes continue to open and compressive stress continues to beapplied through the upward movement of the bulging die element 62 actingupon the lower edge of the inverted cup shaped member 76, the memberbegins to bulge out into the void 78 .as 'shown in FIG. 4 so that itattains the bulged configuration shown in FIG. 4A.

Once the die shoes 12 and 14 have completely opened, the finished bulgedproduct or cup shaped member 76 is wedged within the upper shear ring 18as shown by the dotted lines of FIG. 5. The finished product can lbeejected from the machine simply by operating the control valve 50 tocause the retractable die element to move down upon the top of thefinished element as shown in solid outline in FIG. 5. The apparatus isthen in condition to receive another workpiece.

FIGS. 6-9 show a modified version of the `apparatus in its variousstages of operation corresponding, in general, to those stages ofoperation as illustrated in FIGS. 2-5. According to this modifiedversion, there is provided on the lower die shoe 14 in place of thecentral forming mandrel 64, a two-piece forming mandrel assembly 82.This .assembly comprises a fixed ring shaped member 84 and a movablecentral member 86. The central movable member includes a fiange 88 whichextends out above the top of the fixed ring shaped member 84. The spacebetween the iiange 88 and the top of the fixed ring shaped member 84 isfilled with an elastomeric material 90. Such materials are solid butresiliently fiowable; and they are of constant volume. Thus, as theflange 88 of the central movable member 86 is pressed down upon thefixed ring shaped member 84, the elastomeric material 90 will fiowlaterally out from between them.

There is also provided a fourth hydraulic channel 92 in the lower dieshoe 14 in communication with a piston 94 which acts upwardly upon thecentral movable member 86.

During the closing movement of the die shoes 12 and 14, the piston 94 issubjected to high hydraulic pressure to maintain the central movablemember -86 up from the fixed ring shaped member 84. Operation of theapparatus, as illustrated in FIGS. 6 and 7, is identical with theearlier described version as illustrated in FIGS. 2 and 3. Thus, asshown in FIG. 6, the die shoes 12 and 14 are brought together with theretractable element 20 and the upper 'shear ring 18 together forcingdown the bulging die element 62 While forming a flat sheet metalWorkpiece into an inverted Cup shaped member 76. Thereafter, as shown inFIG. 7, the retractable die element 20 is retracted to leave a void 78into which the cup shaped member 76 is to be bulged. Thereafter, the dieshoes are opened as shown in FIG. 8 so that the bulging die elementbegins to raise as aforedescribed.

At this point in operation, and while the die shoes are still opening,an hydraulic control valve (not shown) is actuated to reduce thepressure in the fourth hydraulic channel 92. This allows the piston 94to yield to the downward force of the upper hold down ring 22. As aresult, the flange 88 of the central movable member 86 is pressed downupon the fixed ring shaped member 84 causing the elastomeric material 90to be squeezed out behind the workpiece material to enhance the bulgingeffect and to ensure that the bulged portion of the workpiece materialwill fully follow the contours of the void 78. After the die shoes arefully opened, of course, the

central movable member 86 will rise to its normal position and theelastomeric material will return to the region between the flange 88 andthe top of the fixed ring shaped member 84.

Having thus described our invention withfparticular reference to thepreferred forms thereof, it will be obvious to those skilled in the artto which the invention pertains, after understanding our invention, thatvarious changes and modifications may be made therein without departingfrom the spiritand scope of our invention, as defined by the claimsappended thereto.

What is claimed as new and desired vto be secured by Letters Patent is:

1. Apparatus for producing bulged container shaped objects from sheetmaterial, said apparatus comprising, an inner die member having outerend and side surfaces for providing substantially complete support forthe interior surfaces of a container shaped object to be formed, a holddown member mounted to press against said sheet material and hold itdown against the end of said inner die member, a retractable formingring dimensioned to extend closely about said inner die member, meansarranged to drive said retractable ring down fully over. sheet materialheld by said hold down member and to draw said sheet material into acontainer shaped about and lying fiatly against said inner die member,said driving means being arranged to retract said forming ringsubsequent to its drawing operation while said hold down membercontinues to press against said sheet material so as to define a givingbulging cavity, a ring shaped bulging element closely embracing saidinner die member and having an outwardly extending edge which engagesthe top edge of the container shaped material on said inner die memberand means for urging said bulging element up toward said hold downmember by lan amount sufficient to bulge said sheet material into theconfiguration of said cavity.

2. Apparatus for producing bulged container shaped objects from sheetmaterial, said apparatus comprising, first and second die shoes mountedfor relative movement valong a given path toward and away from eachother, an inner die member fixedly mounted on one of said shoes andextending out toward the other, said inner die member having outer endand side surfaces for substantially completely supporting the internalsurfaces of a container shaped object formed thereover, a hold downmember yieldably biased to extend outwardly from the other shoe towardthe outer end of said inner die member for clamping sheet materialtherebetween as said die shoes are brought together, a retractable ringdimensioned to fit over said inner die member with sufficient clearanceto draw sheet material down over and closely against said inner diemember, means mounting said retractable ring to move with said othershoe to come down over sheet material and draw same to a container shapeover and fully against said inner die member upon closure of said dieshoes and thereafter to retract said ring off from said inner die memberwhile said shoes remain closed, a ring shaped bulging member dimensionedto fit closely about said inner die member and formed with an innercircumferential step for engaging the edge of a container shaped objectdrawn over said inner die member, said bulging member further includinga lateral surface extending up from said step to provide lateral supportover a portion of the outer side surface of the container shaped object,means yieldably biasing said bulging member to extend .outwardly fromsaid one shoe toward said retractable ring, and a bulging member holddown element extending from said other die shoe and dimensioned toengage and depress said bulging member upon closure of said die shoes,whereby, when said die shoes are closed, said retractable ring formssheet material into a container configuration over said inner die memberwhile said bulging member hold down element depresses said bulgingmember, and thereafter, following retention of the retractable ring,when said die shoes are opened, said hold down member continues to forcesaid container configuration onto said inner die member while saidbulging element moves upwardly to engage the edge of said containerconfiguration for producing bulging of same.

3. Apparatus for bulging container shaped objects said apparatuscomprising, upper and lower die shoes mounted for reciprocal movementalong a givenpath toward and away from each other, an inner die membermounted to` extend from one of said shoes and having outer end andlateral surfaces which fit inside and provide substantially competesupport for the inner bottom and side surfaces, respectively, of acontainer shaped object, hold down means mounted to extend from theother shoe and to engage the outer bottom of said container shaped'object to hold it down over said inner shaped member, said hold `downmeans comprising an extensible die element and yieldably biased mountingmeans urging said element toward an extended position toward inner diemember, ring means arranged to provide lateral support circumferentiallyabout and part way along the outer side surface of lsaid containershaped object, means controlling the longitudinal position of said ringmeans so that it will define the upper limit of a bulge to be formedabout said object, a ring shaped bulging element closely embracing saidinner die member and having an outwardly extending edge which engagesthe top edge of said container shaped object, further yieldably biasedmounting means arranged to urge said bulging element toward said othershoe, and secondary hold down means separate from said ring means andtixedly mounted on said other shoe in a position to engage and depresssaid bulging element upon closure of said shoes while allowing reversemovement of said bulging element upon opening of said shoes while saidhold down means extends to maintain said container shaped object inposition over said inner die member.

4. Apparatus for bulging sheet metal objects, comprising, upper andlower die shoes, a central forming mandrel extending from one of saiddie shoes, an upper hold down mandrel extending from the other of saiddie shoes and aligned with said inner forming mandrel, a retractable dieelement dimensioned to fit around said inner forming mandrel for drawingsheet material thereover, said retractable die element being mounted forlongitudinal reciprocal movement on said other die shoe and enclosingsaid hold down member, means associated with said other die shoe forcontrolling retraction and protraction of said retractable die element,and a bulging element on said one .die shoe immediately surrounding andembracing said inner forming mandrel, said bulging die element having afirst surface which engages the edge of a container shaped object drawnover said inner forming mandrel and further having a lateral surfaceextending longitudinally from said edge catching surface in a directionparallel to the lateral edges of said inner forming mandrel to providelateral support to a portion of the outer edges of an object drawn oversaid inner forming mandrel, and means for causing longitudinal movementof said bulging die element along said forming mandrel after retractionfrom said retractable die element.

5. Apparatus for forming bulged container shaped objects comprisingmeans for drawing a container shaped object from sheet metal includingan inner mandrel and an outer forming ring, said forming ring beingdimensioned and arranged to draw sheet material closely over saidmandrel to lie against the endand sides of the mandrel means for holdingsaid container shaped object onto said mandrel` following such formingring retraction, and a bulging element comprising a bulging ring closelyfitted about said .mandrel and movable therealong to engage the edge ofsaid container shaped object and apply compressive stress to thesides ofsaid object forv causing an outward bulging thereof into the regionvoided by the retraction of said outer forming ring. i

6. Apparatus as in claim 5 wherein said bulging rin has a first radiallyextending surface for engaging the edge of said container shaped objectand a longitudinal surface extending out from said radially extendingsurface in parallel relationship with the sides of said inner mandrel todefine a narrow slot into which the edge region of the container. shapedobject extends.

7. A method for producing from flat sheet material, a container shapedobject having an annular bulge, said method comprising the steps ofdrawing said sheet material tightly over a central mandrel4 by means ofa close fitting ring while holding the central portion of said materialagainst the end of Vsaid mandrel, and, while maintaining the centralportion of said material against the end of said mandrel, withdrawingsaid ring to form a bulging cavity and forcing the drawn edge of saidmaterial back along the surface of `said mandrel to bulge said materialinto said cavity so as to cause the bulged material to assume the shapeof said cavity.

8. In apparatus for forming from flat sheet material, a container shapedobject having an annular bulge, the combination of a composite centralforming mandrel over which a container shaped object may be drawn and abulging ring .which fits closely about the mandrel to engage the edgesof the container shaped object so drawn to push them back along the sidesurfaces of the mandrel to produce a bulging of the object, saidcomposite central forming mandrel comprising a central member and anouter ring shaped member arranged coaxially for separately controlledlongitudinal movement, said central member having an outer flange likeformation which extends over the end of the ring shaped member to definebetween the two a compressible annular cavity, and an elastomericsubstance filling said cavity.

9. Apparatus as in claim 8 further including a forming ring forinitially drawing a container shaped object from flatsheet material downover said mandrel and means for maintaining said central member and saidouter ring shaped member in a xed axial displacement during movement ofsaid forming ring.

`References Cited FOREIGN PATENTS 12/ 1868 Great Britain.

RICHARD J. HERBST, Prfmafy Examiner.

